Nistune Forums

Hi guys ! I have an issue that is very strange, I have checked my fuel pressure and it is ok every time so, here is the problem.

on full throttle at about 2000-4000rpm everything is ok, good afr, but at the time the ECU switch to semi sequential ( injection time divided by 2 ) the car goes from 12 to 15 AFR... Here is my log where you can see it . and of course the .bin that comes with

anyone have an idea ??
thank you.

so... the car is backfireing is that it ?

something like "vvvrrruuuummmmmmm poc poc poc vvvrruuuuummmmm poc poc " and so on...?

absolutely not, the car is just running too lean so I stop pushing the gas pedal ....

I'll have a look over this log tonight. Heard of a similar issue once before

what are the rest of the specs of the setup ?
I took a brief look at the log and is indeed "weird"... need to take a better look at it before getting to rough conclusions.

Setup of my car

full forged CA18DET ( crank / rod /pistons )

tomei 260/10.25mm cams with tomei springs and solid lifters

garrett GT3071 A/R .86 T25 turbo

RC 1200cc fuel injectors ( 1090cc @ 3bar fuel pressure )

Z32 AFM

on the log I am at only 1bar of boost pressure, the car made previously 415whp at 1.6bar and runs fines for about 4500km before this thing happens.

I have tried another ECU with just an eprom on it, and the problem is also there ...

I had this issue which ended up being spark jumping out of the wires with a z31 setup.

thank you for that, but I thought it will go richer if spark is not good ...

Thank fully not.... If a miss fire occurs more oxygen is pumped into the exhaust.
Almost always see a sporatic lean condition usually very short but noticeable if you know when the miss happened.

In Boosted engines a torque plateau on the graphs will appear.
If monitoring manifold pressure also a similar plateau in the boost graphs.

I have tried another complete set of coil pack with perfect wires, and same thing happens ...

I'm thinking that it is my injectors that creates the problem ...

I have made an awfful fuel map to correct it and it works .... It is like the injectors have too much lag and when semi sequential injection occurs the latency must be two times as usual ...

to have 12.0 AFR all the time I must ask 12.0 AFR until 3800rpm and at 4000 I ask 9.0 AFR then climbing to 12.0 @ 7500rpm proportionaly ...

I will bought BOSCH 1600cc injectors and sell this set of PL9 1200 RC injectors ..

Do you have a boost dyno graph also?
Might be worth testing the rising rate fuel pressure regulator to ensure it increases with boost accordingly.

streetbike wrote:I have tried another complete set of coil pack with perfect wires, and same thing happens ...

I'm thinking that it is my injectors that creates the problem ...

I have made an awfful fuel map to correct it and it works .... It is like the injectors have too much lag and when semi sequential injection occurs the latency must be two times as usual ...

to have 12.0 AFR all the time I must ask 12.0 AFR until 3800rpm and at 4000 I ask 9.0 AFR then climbing to 12.0 @ 7500rpm proportionaly ...

I will bought BOSCH 1600cc injectors and sell this set of PL9 1200 RC injectors ..

Have you logged you AFM voltage? If the AFM is too close to the turbo, it might create some turbulance etc. It's often worst at the point where turbo is just starting to spool up, then works ok when full boost..